Petrology and SHRIMP zircon geochronology of granulites from Vesleknausen, L眉tzow-Holm Complex, East Antarctica: Neoarchean magmatism and Neoproterozoic high-grade metamorphism
详细信息 查看全文
- 作者：Toshiaki Tsunogae ; Daniel J. Dunkley ; Kenji Horie ; Takahiro Endo ; Tomoharu Miyamoto ; Mutsumi Kato
- 关键词：Granulite ; Charnockite ; SHRIMP zircon geochronology ; Pseudosection ; Rundvå ; gshetta ; Gondwana supercontinent
- 刊名：Geoscience Frontiers
- 出版年：March, 2014
- 年：2014
- 卷：5
- 期：2
- 页码：167-182
- 全文大小：4578 K
文摘
We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the L眉tzow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss), mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750-850聽掳C, approximately 150聽掳C lower than those estimated for metasedimentary gneisses from Rundv氓gshetta, 6聽km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9聽卤聽7.4聽Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548聽Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundv氓gshetta-Vesleknausen-Strandnibba region in southwestern L眉tzow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5聽Ga arc magmatism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern L眉tzow-Holm Bay) by subduction/collision events during the assembly of Gondwana supercontinent, and subsequently underwent 鈭?50聽掳C granulite-facies metamorphosed during Neoproterozoic to Cambrian final collisional event.